Alarm over shop's high Carbon Monoxide levels - Victoria, Australia

[DandyDon]

I have two CO detectors/alarms in my home; the wall-mounted ones are pretty cheap, around $30. I had just assumed those wouldn't really work for scuba.

Right, they won't work in the 0 to 10 ppm range needed.

As far as the once-per-day checks, I decided to do 2-minutes of research and discovered you can get an inline model for about $500. Now, $500 might be a lot for an individual scuba-diver, but for fill-station that is CHEAP! Much better than demanding your potentially unreliable employees to check the CO 1-2x per day, which they'll probably skip. I retract my once-per-day idea as pretty silly.

That would be good for a small fill shack, but the 0.5-1 L/min flow rate might be limiting for larger compressors. Analox gave a larger, more costly unit to the main fill shack in Cozumel, and the tank jockeys disabled the automatic shutoff.

One member here actually has a Sensorcon CO unit attached to his home compressor.

Instead of dumping straight from the tank into the bag, I have an air-gun which attaches to a BCD hose in my save-a-dive-kit. That requires attaching some regulators of course, but maybe more reliable and less annoying than trying to control a bag and a tank-valve.

How fancy. The bag trap seems simpler to me, but since you have it, ok.

I also considered this wall-mount unit, it's about $30. I may still buy this unit for my home, because my other CO-alarms are just alarms, and have no display of CO-levels. In the normal mode, it won't show below 30ppm, but you can push a button and see below 30ppm. Anyone looking for something dual-use, I'd probably go with that model.

Plugin with battery backup is great. That page contradicts itself on whether it uses AA or 9V batteries, but either is fine. I don't know how accurate it is in the push-button lower range or where you saw that, but Kidde is a top brand.

That said, I went with the "walmart" one you mentioned. Here's the Amazon link for anyone else who might be interested. Reviews seem to suggest quality is "ok", not amazing, and it appears to be one of those generic devices that gets rebranded by a bunch of companies. That said, it is intended for "real time" monitoring, and intended for checking very low PPM levels, so it'll probably be better for quickly checking tanks.

Yeah, it's a generic unit sold by many Asian sources. There was another one linked on that page for $7 less, but they're all cheap. I question how long 3 AAAs would last in the always-on function, so let us know when you test it. I see that it claims a three-year sensor life, but I would write the purchase date on the back with an indelible marker and replace it after a year.

 

[Storker]

Total disregard for human life; one would not expect this type of incident to happen in a developing nation. Yet, it occurred through the absence of defensible action by service technicians not reporting a lapse in communication with relevant authorities.

Well, stuff happens and sh*t managers are found all over the world. Even in the land of the free and the brave, which to many non-US folks sometimes present as a developing, not a developed country. If you're surprised that sh*t managers exist also in AUS, I'd recommend that you update your worldview.

 

[John C. Ratliff]

As an industrial hygienist, we in that field have been using detector tubes to initially test for gases like carbon monoxide. Detector tubes, once you are set up with a hand pump and the tubes, are pretty easy to use and read. They usually have a plus or minus 20% accuracy, and can be bought to detect in the 0-10 ppm range.

Detector Tubes And When To Use Them - Interscan Corporation

Discussion of detector tubes--graduated glass tubes filled with a chemical reagent, that can be used for semi-quantitative analysis of gases.

www.gasdetection.com

I would be leery of using a CO analyzer from a retail store or Amazon what is really cheap. Why? Well, They say that they have “automatic calibration,” but in our industrial hygiene work, we usually for legal purposes have to calibrate our instrument with a reference gas both before and after the measurements are taken. That way, we know that the sample has been measured by an instrument that is in calibration.

For diving purposes, I can see how these CO detectors would be useful, especially when diving on a live-aboard or in a foreign country. But realize that no matter the manufacturer’s specs and saying that they have “automatic calibration,” I doubt any of that would hold up in court if something were to happen. Use them solely as an indicator.

If you want to calibrate your instrument, you can buy a small cylinder of referenec CO gas at 50 ppm. That way you would know that your instrument is actually reading correctly.

CO 50 ppm/ Air Gasco Equivalent 34LS-50 34 Liter calibration gas

Shop E-Gas depot for a 34 Liter- Carbon Monoxide 50 ppm Air Gasco Equivalent 34LS-50 calibration gas. You'll find a variety of calibration gases, including hydrogen sulfide, carbon monoxide, pure methane and cylinder sizes ranging from 11L to 850L.

egasdepot.com

One other thing, here are the Recommended Exposure Limit (REL) and the Permissible Exposure Limit (PEL) for carbon monoxide from NIOSH and OSHA, respectively:

NIOSH REL​

TWA 35 ppm (40 mg/m3) C 200 ppm (229 mg/m3)

OSHA PEL​

TWA 50 ppm (55 mg/m3) See Appendix G

IDLH
1200 ppm
See: 630080

CDC - NIOSH Pocket Guide to Chemical Hazards - Carbon monoxide

Carbon oxide, Flue gas, Monoxide Colorless, odorless gas. [Note: Shipped as a nonliquefied or liquefied compressed gas.]

www.cdc.gov

These are 8-our exposure limits that a worker could be exposed to routinely on a job; they are not for diving at all. Note that the “C 200 ppm (229 mg/m3)“ is a “Ceiling Limit,” or a limit which cannot be exceeded during a workday. Also note that the IDLH level (Immediately Dangerous to Life and Health) is 1200 ppm. If you get into an environment where your instrument is reading 1,000 ppm, get out immediately.

SeaRat

 

[SlugLife]

As an industrial hygienist...

SeaRat

That's good info, thanks for sharing. Obviously, it won't hold up in court, my main concern is whether it would be enough to detect and flag a potentially dangerous tank. Like you said, "solely as an indicator."

In other words, I would expect all of my tanks to read zero. However, lets say my cheap detector shows 2ppm or higher; that's probably enough to pass on that tank, and demand a refill, although perhaps not good enough for a court or anything scientific. If we're to be generous, that 2ppm, might be 6ppm, but regardless it should at least prevent me from breathing in 10ppm+ tanks.

 

[DandyDon]

Detector tubes, once you are set up with a hand pump and the tubes, are pretty easy to use and read.

That's a very interesting article you linked. Some of it is beyond my paygrade in reading, but I read over it and saw several points that would rule out trying to use it at a dive site or on a moving boat. Still, an interesting alternative view in CO testing.

I would be leery of using a CO analyzer from a retail store or Amazon what is really cheap. Why? Well, They say that they have “automatic calibration,” but in our industrial hygiene work, we usually for legal purposes have to calibrate our instrument with a reference gas both before and after the measurements are taken.

Yep, the actual readings are nothing to take seriously, and the cheap units can be used only as a fail-safe. And forget the three-year lifespan of the unit and replace it annually. The Sensorcon unit would be better, but until we can get every diver testing every tank everywhere, they are a start and better than nothing.

If you want to calibrate your instrument, you can buy a small cylinder of referenec CO gas at 50 ppm.

That would not be allowed to fly to a dive destination, but it'd be interesting to test units before a trip to see how accurate they are. I guess I'd need a valve too?

These are 8-our exposure limits that a worker could be exposed to routinely on a job; they are not for diving at all. Note that the “C 200 ppm (229 mg/m3)“ is a “Ceiling Limit,” or a limit which cannot be exceeded during a workday. Also note that the IDLH level (Immediately Dangerous to Life and Health) is 1200 ppm. If you get into an environment where your instrument is reading 1,000 ppm, get out immediately.

Yeah, comparing work place limits and scuba tank limits are night and day different.

However, lets say my cheap detector shows 2ppm or higher; that's probably enough to pass on that tank, and demand a refill, although perhaps not good enough for a court or anything scientific. If we're to be generous, that 2ppm, might be 6ppm, but regardless it should at least prevent me from breathing in 10ppm+ tanks.

No, with "Accuracy: CO: ±5% or ±10PPM" on the cheapest units, 2ppm might mean 12ppm or nothing. It's just a ballpark tool to keep you from diving questionable tanks.

 

[John C. Ratliff]

Dandy Don, the workplace limits, and especially the IDLH limit for CO of 1200 ppm, was quoted to note that if a diver is below decks, and near the compressor and gets a high reading (say approaching 1,000 ppm), they should get out of there immediatly, and evacuate anyone else who’s there. It was not meant for tanks.

SeaRat

 

[DandyDon]

Dandy Don, the workplace limits, and especially the IDLH limit for CO of 1200 ppm, was quoted to note that if a diver is below decks, and near the compressor and gets a high reading (say approaching 1,000 ppm), they should get out of there immediatly, and evacuate anyone else who’s there. It was not meant for tanks.

SeaRat

Oh, yeah, for sure. I wonder how many boats have CO alarms tho? They should now that the technology is available and affordable, as homes should, but progress is needed still.

 

[poseident]

I suspect this happens a lot more frequently that people realize.

The last time I had an issue was back in the mid-90s when tanks from a well-known shop at a famous destination always had a "taste" and gave me a headache. I paid close attention on my next trip, and noticed the intake for the compressor was sticking out of the wall on the same side of the shop as their dock, where boats sat with outboards chugging all morning. After a conversation with the owner, they moved the intake and problem solved. But thousands of divers went through there prior to the fix. Happily there was never a serious incident. Perhaps I'm especially sensitive to CO...

My point is, generally speaking, lots of accidents happen because "nobody noticed" whatever the problem was.

 

[DandyDon]

The last time I had an issue was back in the mid-90s when tanks from a well-known shop at a famous destination always had a "taste" and gave me a headache.

I remember a double fatality at a popular Roatan resort a few years ago when a Texas tourist and a popular local DM died, and the resort tried to blame the Texan for drowning the DM. Their attempt failed, the truth came out, the widow sued - however difficult that was in Honduras, and settled with a nondisclosure agreement.

My point is, generally speaking, lots of accidents happen because "nobody noticed" whatever the problem was.

Survivors usually accept that it's Traveler's Flu and the others written off as Drownings.

 

[poseident]

Survivors usually accept that it's Traveler's Flu and the others written off as Drownings.

That's a fair point. I myself dismissed the first time this happened to me as "I'm probably dehydrated." But not the second time....